System and method for detecting occlusions in an infusion pump

Abstract

Occlusions in a delivery line of an infusion pump can be detected by measuring pressure differentials in the pump over short periods of time in order to minimize the effects of long term systematic sensor changes. In a delivery mode such as basal insulin delivery where a small portion of a volume of fluid is delivered, pressure readings can be obtained before and after the motor move to deliver each portion and compared. The differentials after one or more motor moves can be compared to determine whether an occlusion is present. In a delivery mode such as bolus insulin delivery in which an entire volume of fluid is delivered, pressure differentials can be obtained for consecutive deliveries at a common point in the delivery cycle of each delivery. Comparison of these pressure values can be used to determine whether an occlusion is present.

The invention claimed is: 
     
       1. An ambulatory infusion system, comprising:
 a disposable infusion cartridge, the infusion cartridge including a collapsible reservoir for containing a fluid and a substantially rigid shell disposed over the collapsible reservoir and forming, an interior volume between an outside surface of the collapsible reservoir and an inside surface of the shell, the disposable infusion cartridge further including a delivery mechanism having a spool slidingly disposed in a bore, the spool including as main section and a distal section axially displaceable relative to the main section with a collapsible volume formed between a seal on the main section and a seal on the distal section; 
 a pump device configured to selectively receive the infusion cartridge and cooperate with the infusion cartridge to deliver fluid from the reservoir to the patient, the pump device including a drive mechanism powered by a motor and selectively engageable with the spool to impart controlled axial movements to the spool to deliver fluid from the cartridge to the patient 
 a pressure sensor located in one of the infusion cartridge and the pump, the pressure sensor in communication with the interior volume of the infusion cartridge; and 
 a processor located in one of the infusion cartridge and the pump wherein the processor is adapted to:
 obtain a first pressure reading of the pressure in the interior volume of the cartridge from the pressure sensor; 
 obtain a second pressure reading of the pressure in the interior volume of the cartridge from the pressure sensor following an operation configured to deliver fluid from the cartridge to a patient; 
 compare the first pressure reading to the second pressure reading; 
 determine, from the comparison, of the first pressure reading to the second pressure reading, whether the distal section of the spool moved axially at time during the operation configured to deliver fluid from the cartridge to the patient when the distal section should have remained stationary; 
 selectively generate an occlusion alarm based on the comparison of the first pressure reading to the second pressure reading if it is determined that the distal section moved at the time it should have remained stationary. 
 
 
     
     
       2. An ambulatory infusion system, comprising:
 a disposable infusion cartridge, the infusion cartridge including a collapsible reservoir for containing a fluid and a substantially rigid shell disposed over the collapsible reservoir and forming an interior volume between an outside surface of the collapsible reservoir and an inside surface of the shell, the disposable infusion cartridge further including a delivery mechanism having a spool slidingly disposed in a bore, the spool including a main section and a distal section axially displaceable relative to the main section with a collapsible volume formed between a seal on the main section and a seal on the distal section; 
 a pump device configured to selectively receive the infusion cartridge and cooperate with the infusion cartridge to deliver fluid from the reservoir to the patient, the pump device including a drive mechanism powered by a motor and selectively engageable with the spool to impart controlled axial movements to the spool to deliver fluid from the cartridge to the patient; 
 a pressure sensor located in one of the infusion cartridge and the pump, the pressure sensor in communication with the interior volume of the infusion cartridge; and 
 a processor located in one of the infusion cartridge and the pump, wherein the processor is adapted to:
 actuate the motor to deliver a portion of fluid contained in the collapsible volume; 
 obtain a first pressure reading of the pressure in the interior volume of the Cartridge from the pressure prior to actuating the motor; 
 obtain the a second pressure reading of the pressure in the interior volume of the cartridge from the pressure sensor after the motor is powered down following actuation; 
 compare the first pressure reading to the second pressure reading; and 
 selectively generate an occlusion alarm based on the comparison of the first pressure reading to the second pressure reading if the second pressure reading is not the same as the first pressure reading. 
 
 
     
     
       3. The system of  claim 2 , wherein the first pressure reading is obtained immediately prior to actuating the motor and the second pressure reading is obtained immediately after the motor is powered down following actuation. 
     
     
       4. The system of  claim 2 , wherein the processor is further adapted to generate the occlusion alarm only if the second pressure reading is not the same as the first pressure reading and at least one previously obtained pressure reading. 
     
     
       5. The system of  claim 2 , wherein the second pressure reading is not the same as the first pressure reading if it is not within a predetermined threshold of the first pressure reading. 
     
     
       6. An ambulatory infusion system, comprising:
 a disposable infusion cartridge the infusion cartridge including a collapsible reservoir for containing a fluid and a substantially rigid shell disposed over the collapsible reservoir and forming an interior volume between an outside surface of the collar reservoir and an inside surface of the shell, the disposable infusion cartridge further including a delivery mechanism having a spool slidingly disposed in a bore, the pool including a main section and a distal section axially displaceable relative to the main section with a collapsible volume formed between a seal on the main section and a seal on the distal section; 
 a pump device configured to selectively receive the infusion cartridge and cooperate with the infusion cartridge to deliver fluid from the reservoir to the patient, the pump device including a drive mechanism powered by a motor and selectively eneageable with the spool to impart controlled axial movements to the spool to deliver fluid from the cartridge to the patient; 
 a pressure sensor located in one of the infusion cartridge and the pump, the pressure sensor in communication with the interior volume of the infusion cartridge; and 
 a processor located in one of the infusion cartridge and the pump, wherein the processor is adapted to:
 actuate the motor to deliver all fluid contained in the collapsible volume to the patient; 
 obtain a first pressure reading of the pressure in the interior volume of the cartridge from the pressure sensor at a time prior to all of the fluid being delivered; 
 obtain a second pressure reading of the pressure in the interior volume of the cartridge from the pressure sensor at a time after all of the fluid has been delivered; 
 compare the first pressure reading to the second pressure reading; and 
 selectively generate an occlusion alarm based on the comparison of the first pressure reading to the second pressure reading if the second pressure reading is the same as the first pressure reading. 
 
 
     
     
       7. The system  claim 6 , wherein the first pressure reading is obtained prior to delivering any of the fluid and the second pressure reading is obtained prior to subsequent actuation of the motor to deliver a subsequent amount of fluid that has been drawn from the collapsible reservoir into the bore. 
     
     
       8. The system of  claim 6 , wherein the first pressure reading is made during a first fluid deliver cycle and the second pressure reading is made during a subsequent fluid delivery cycle, and each reading is taken at a common point in the respective delivery cycle. 
     
     
       9. The system of  claim 6 , wherein the processor is further adapted to generate the occlusion alarm only if the second pressure reading is the same as the first pressure reading and at least one previously obtained pressure reading. 
     
     
       10. The system of  claim 6 , wherein the second pressure reading is not the same as the first pressure reading if it is not within a predetermined threshold of thefirst pressure reading. 
     
     
       11. An ambulatory infusion stem, comprising:
 a disposable infusion cartridge, the infusion cartridge including a collapsible reservoir for containing a fluid and a substantially rigid shell disposed over the collapsible reservoir and forming an interior volume between an outside surface of the collapsible reservoir and in inside surface: of the shell, the infusion cartridge further defining a collapsible volume for receiving fluid from the collapsible reservoir; 
 a pump device including a motor and configured to selectively receive the infusion cartridge and cooperate with the infusion cartridge to deliver fluid from the reservoir into the collapsible volume and to the patient; 
 a pressure sensor located in one of the infusion cartridge and the pump, the pressure sensor in communication with the interior volume of the infusion cartridge; and 
 a processor located in one of the infusion cartridge and the pump, wherein the processor is adapted to:
 actuate the motor to deliver fluid contained in the collapsible volume to the patient; 
 obtain a first pressure reading of the pressure in the interior volume of the cartridge from the pressure sensor prior to actuating the motor; 
 cease actuation of the motor after delivering a desired amount of the fluid from the collapsible volume; 
 obtain a second pressure reading after ceasing actuation of the motor; 
 compare the first pressure reading to the second pressure reading; and 
 generate an occlusion alarm if the second pressure reading is not the same as the first pressure reading. 
 
 
     
     
       12. The system of  claim 11 , wherein the first pressure reading is obtained immediately prior to actuating the motor and the second pressure reading is obtained immediately after ceasing actuation of the motor. 
     
     
       13. The system of  claim 11 , wherein the processor is further adapted to generate the occlusion alarm only if the second pressure reading is not the same as the first pressure reading and at least one previously obtained pressure reading. 
     
     
       14. The system of  claim 11 , wherein the second pressure reading is not the same as the first pressure reading if it is not within a predetermined threshold of the first pressure reading. 
     
     
       15. The system of  claim 11 , wherein the processor is adapted to deliver only a portion of the fluid in the collapsible volume between actuating the motor and ceasing actuation of the motor. 
     
     
       16. An ambulatory infusion system, comprising:
 a disposable infusion cartridge, the infusion cartridge including:
 a collapsible reservoir for containing a fluid; 
 a substantially rigid shell disposed over the collapsible reservoir and forming an interior volume between an outside surface of the collapsible reservoir and an inside surface of the shell; and 
 a delivery mechanism having a spool slidingly disposed in bore, the spool including a main section and a distal section axially displaceable relative to the main section with a collapsible volume formed between a seal on the main section and a seal on the distal section; 
 
 a pump device configured to selectively receive the infusion cartridge, the pump device including a drive mechanism powered by a motor and selectively engageable with the spool to impart controlled axial movements of the spool to deliver fluid from the reservoir into the collapsible volume and to a patient; and 
 a processor located in one of the infusion cartridge aid the pump, wherein the processor is adapted to
 actuate ail operation to deliver fluid stored in the collapsible volume to the patient; 
 determine whether the distal section of the spool moved axially at a time during the operation configured to deliver fluid from frond the reservoir to the patient when the distal section should have remained stationary; and 
 generate an occlusion alarm if it is determined that the distil section moved at the time it should have remained stationary. 
 
 
     
     
       17. The system of  claim 16 , further comprising a pressure sensor located in one of the infusion cartridge and the pump, the pressure sensor in communication with the interior volume of the infusion cartridge and wherein the processor is further adapted to:
 obtain a first pressure reading of the pressure; in the interior volume of the cartridge from the pressure sensor; 
 obtain a second pressure reading of the pressure in the interior volume of the cartridge from the pressure sensor following the operation configured to deliver fluid from the reservoir to a patient; 
 compare the first pressure reading to the second pressure reading; and 
 selectively generate the occlusion alarm based on the comparison. 
 
     
     
       18. The system of  claim 17 , wherein the processor is further adapted to determine that the distal section of the spool moved and generate the alarm if the second pressure reading is not the same as the first pressure reading.